This invention relates to a new substance having anti-tumour activity, a process for producing the same by fermentation and an antitumour composition containing the same.
It was previously known to produce mitomycin A and/or B by fermentation, which process comprises culturing a microorganism of Streptomyces caespitosus or mutant strain thereof in a medium to accumulate mitomycin A and/or B in the cultured liquor and recovering mitomycin A and/or B therefrom. In this case, the filtrate of the cultured liquor is treated by using active carbon to adsorb the active substances which are then extracted with a solvent such as acetone, pyridine and the like. The extracted solution is concentrated and the active substances are extracted from the concentrated solution with various organic solvents. Alternatively, the cultured liquor is treated with various organic solvents and the solution containing the active substances is added with anhydrous sodium sulfate and concentrated. It is also possible to adsorb the active substances with active alumina and extracted with various organic solvents.
The present invention is based upon the discovery that a new substance having anti-tumour activity, designated by us as AX-2, may be obtained by treating the filtrate of the cultured broth of a strain of Streptomyces caespitosus.